An osteon contains

The storehouse of calcium ions in the muscle fibre is

Arrange the given steps of muscle contraction in the series of events from first to last.
$I.$ Myosin head binds to the exposed active site on actin to form a cross bridge.
$II.$ The $Z$-line attached to these actin are also pulled inwards,thereby causing shortening of sarcomere,also called contraction.
$III.$ This pulls the attached actin filaments towards the centre of $A$-band.
The correct option is:

The contractile unit of a muscle fiber is known as:

Contraction of muscle fibre takes place by the sliding of $:-$

What do ligaments connect?